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Composite membranes and methods for making same

a technology of composite membranes and membranes, applied in the field of composite membranes, can solve the problems of poor mechanical integrity, poor flux, and high cost of supporting membranes, and achieve the effects of increasing the h2 flux, high permselectivity for h2, and increasing the resistance to thermal cycling and/or mechanical loads

Active Publication Date: 2007-11-08
INTEGRATED DEVICE TECH INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] In view of the foregoing, it is a primary objective of the present invention to provide a composite membrane, where the composite membrane has improved resistance to thermal cycling. A further objective is to provide a composite membrane having improved mechanical reliability. It is a further objective to provide a composite membrane having improved adhesion of the active layer to the support structure. It is another objective of the present invention to provide a composite membrane having a high permselectivity for a gas species of interest, such as H2. It is another objective of the present invention to provide a composite membrane that is attached to a metal rim for low cost and convenient sealing and integration of membranes into membrane modules and separating systems.
[0014] One or more of the foregoing objectives and advantages may be realized according to the present invention, which in one aspect provides a composite membrane comprising a porous support structure and one or more active layers disposed within the pores of the support structure. According to this aspect, the thin active layer can facilitate high permeance of a gas species even as the support structure can be of much greater thickness to provide required mechanical integrity over a wide pressure range.

Problems solved by technology

Although Pd-based bulk foils exhibit near-infinite selectivity for H2, they are expensive and have poor flux due to the required foil thickness.
However, the fabrication of thin-film Pd supported membranes that have the required defect-free structure requires a Pd thickness of at least 10 μm to 50 μm, which is too thick for many applications, such as H2 separation in portable fuel cell reformers.
Furthermore, the reliability of supported membranes is limited by the poor mechanical integrity of the thin metal layers deposited onto the porous support.
Further, the poor mechanical integrity is often exacerbated by temperature cycling and / or mechanical loads that are encountered in use.
Also, the reliable sealing of thin supported membranes is also challenging and the cost of the manufacturing and integration of such membranes has hindered their widespread application.
However, the total area of the supported Pd membrane was small, limiting the total flux.
Additionally, the Pd windows ruptured when subjected to transmembrane pressures of about 0.5 bar, and the thermal reliability of the thin Pd film on Si was a problem due to the mismatch of temperature expansion coefficients.
Although thin-film supported membranes, such those described above for H2 separation, have been fabricated, their commercial utility has not been realized.
Such membranes have problems related to poor adhesion of the Pd layer to the support, damage to the Pd layer caused by thermal cycling and susceptibility to damage from mechanical abrasion
However, although these membranes could provide much thinner active layer, the active layer is still on the membrane surface and is prone to hydrogen embrittlement and mechanical damage.
The method does not allow the formation of the active layer disposed entirely within the nanoporous support structure.

Method used

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  • Composite membranes and methods for making same
  • Composite membranes and methods for making same
  • Composite membranes and methods for making same

Examples

Experimental program
Comparison scheme
Effect test

example 1

Blank Symmetric and Asymmetric Membranes

[0108] Blank AAO symmetric and asymmetric support membranes are formed by anodizing 99.99% pure Al foil that is rolled and pressure-annealed at 350° C. and 5,000 psi for 20 min. The resulting Al foil is cleaned and anodized on both sides in 1% oxalic acid electrolyte at a temperature of 10° C. and an anodization current density of 10 mA / cm2, until a charge density of 20 C / cm2 is accumulated. The resulting layer of aluminum oxide is then stripped in a hot solution of 200 g / l chromic oxide in 50% phosphoric acid, the Al substrate is rinsed and dried, and an adhesion layer of 0.5 μm of AAO is grown using the same conditions.

[0109] Conventional photoresist is applied to both sides of the Al substrate, is soft-baked at 90° C. for 20 min and is exposed to a UV light using a mask with the openings of required size and format to define the number, the location, the size and the format of the membranes—in this case, four 25 mm circular membranes on e...

example 2

Blank Symmetric and Asymmetric Membranes with an Al Rim

[0112] Blank AAO symmetric and asymmetric membranes are produced using Al foil prepared and patterned as noted in Example 1, except only one size of Al substrate is patterned with 13 mm membranes. Anodization is carried out in 3% oxalic acid electrolyte at a temperature of 12° C. and an anodization voltage of 40V until a charge density of 200 C / cm2 is accumulated, resulting in 100 μm thick AAO films with 37 nm pores. With some Al substrates, voltage reduction profile #2 (described above) is used to bring the anodization voltage down to 4 V, and anodization is continued for 100 seconds at 4V. The resulting asymmetric AAO has a final pore diameter of about 5 nm.

[0113] The resulting AAO supports, which are still attached to Al, are masked with 3M electroplating tape to define 8 mm circles in the center of the 13 mm membranes. The barrier layer in the exposed area was breached in a solution of concentrated hydrochloric acid at −2°...

example 3

Composite AAO / Pd Membranes with Al rim for H2 Separation

[0114] Blank AAO membranes on Al foil are produced as previously noted in Example 2, except the process is stopped before masking for breaching of the barrier layer. Electrodeposition of a Cu sacrificial layer is carried out in an aqueous solution of 0.5M CuSO4 for 1000 seconds in potentiostatic mode using a 100 Hz sinusoidal waveform with an amplitude of ±9V and a DC offset of −0.5V. Electrodeposition of the active layer of Pd nanoplugs is carried out in a commercial PallaSpeed electrolyte (Technic) for 500 seconds in potentiostatic mode using a 100 Hz SINE waveform with an amplitude of ±9V and a DC offset of −0.5V. A backside of the Al foil opposite to the AAO support is masked to define an 8 mm circle and exposed Al is etched using a solution of 20% hydrochloric acid and 15% CuCl2 in water, until the backside of AAO / Pd / Cu membrane is exposed. The barrier layer is etched for 20 to 30 minutes in a solution of 0.5M of phosphor...

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Abstract

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 60 / 767513, filed on May 7, 2006, which is incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY-FUNDED RESEARCH [0002] This invention was funded by the National Science Foundation under Grant No. DMI-0420147 (Phase I) and Grant No. OII-0548757 (Phase II), and by the Department of Energy under Grant No. DE-FG02-04ER84086, both administered by the Small Business Innovation Research (SBIR) program. The Government has certain rights in this invention.BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to composite membranes, methods for making composite membranes and applications of the composite membranes. The composite membranes include a porous support structure and one or more active layers disposed within the pores of the support structure. [0005] 2. Description of Related Art [0006] Ef...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01D53/22
CPCB01D53/228B01D67/0062B01D2325/021B01D2325/06C01B2203/1223C01B3/323C01B2203/0233C01B2203/041C01B3/12Y02P20/52B01D2325/0212
Inventor ROUTKEVITCH, DMITRIPOLYAKOV, OLEG G.
Owner INTEGRATED DEVICE TECH INC
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